Bsi bs en 01504 9 2008 (2009)

BRITISH STANDARD Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity Part 9: General principles for use of products and systems ICS 01.040.91; 91.080.40 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 1504-9:2008 BS EN 1504-9:2008 National foreword This British Standard is the UK implementation of EN 1504-9:2008 It supersedes DD ENV 1504-9:1997 which is withdrawn The UK participation in its preparation was entrusted to Technical Committee B/517/8, Protection and repair of concrete structures A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2009 © BSI 2009 ISBN 978 580 61618 Amendments/corrigenda issued since publication Date Comments BS EN 1504-9:2008 EUROPEAN STANDARD EN 1504-9 NORME EUROPÉENNE EUROPÄISCHE NORM September 2008 ICS 01.040.91; 91.080.40 Supersedes ENV 1504-9:1997 English Version Products and systems for the protection and repair of concrete structures - Definitions, requirements, quality control and evaluation of conformity - Part 9: General principles for the use of products and systems Produits et systèmes pour la protection et la réparation de structures en béton - Définitions, exigences et mtrise de la qualité et évaluation de la conformité - Partie 9: Principes généraux d'utilisation des produits et systèmes Produkte und Systeme für den Schutz und die Instandsetzung von Betontragwerken - Definitionen, Anforderungen, Qualitätsüberwachung und Beurteilung der Konformität - Teil 9: Allgemeine Grundsätze für die Anwendung von Produkten und Systemen This European Standard was approved by CEN on 27 July 2008 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 © 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members B-1050 Brussels Ref No EN 1504-9:2008: E BS EN 1504-9:2008 EN 1504-9:2008 (E) Contents Page Foreword Introduction Scope Normative references Terms and definitions 4.1 4.2 4.3 Minimum requirements before protection and repair General Health and Safety Assessment of defects and their causes 5.1 5.2 5.3 5.4 Protection and repair within a structure management strategy .9 General Options Factors Choice of appropriate strategy 10 6.1 6.2 Basis for the choice of protection and repair principles and methods 10 General 10 Principles and methods of protection and repair 10 7.1 7.2 Properties of products and systems required for compliance with the principles of protection and repair 13 General 13 Methods which not make use of specific products and systems .13 Maintenance following completion of protection and repair 13 Health, safety and the environment 13 10 Competence of personnel 13 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Annex A (informative) Guidance and background information 15 Introduction .15 A.1 Scope 15 A.2 Normative reference 16 A.3 Terms and definitions 16 A.4 Minimum requirements before protection and repair 16 A.5 Protection and repair within a structure management strategy .20 A.6 Basis for the choice of protection and repair principles and methods 22 A.7 Properties of products and systems required for compliance with the principles of protection and repair 27 A.8 Maintenance following completion of protection and repair 28 A.9 Health, safety and environment 28 A.10 Competence of personnel 28 Bibliography 29 BS EN 1504-9:2008 EN 1504-9:2008 (E) Foreword This document (EN 1504-9:2008) has been prepared by Technical Committee CEN/TC 104 “Concrete and related products”, the secretariat of which is held by DIN This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by March 2009, and conflicting national standards shall be withdrawn at the latest by March 2009 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights It has been prepared by Sub-committee "Products and systems for the protection and repair of concrete structures” (Secretariat AFNOR) This document supersedes ENV 1504-9:1997 Modifications to ENV 1504-9:1997 are: a) Status of document changed form pre-standard to standard; b) Editorial and technical modifications in those cases where necessary ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ This document is one part of the European Standard on “Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity” The other parts are listed below:  Part 1: Definitions  Part 2: Surface protection systems for concrete  Part 3: Structural and non-structural repair  Part 4: Structural bonding  Part 5: Concrete injection  Part 6: Anchoring of reinforcing steel bar  Part 7: Reinforcement corrosion protection  Part 8: Quality control and evaluation of conformity  Part 10: Site application of products and systems and quality control of the works According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom BS EN 1504-9:2008 EN 1504-9:2008 (E) Introduction Protection and repair of concrete structures require complex design work This European Standard defines the principles for protection and repair of concrete structures which have suffered or may suffer damage or deterioration and gives guidance on the selection of products and systems which are appropriate for the intended use This European Standard identifies key stages in the repair process:  assessment of the condition of the structure;  identification of the causes of deterioration;  deciding the options for protection and repair;  selection of the appropriate principle(s) of protection and repair;  selection of methods;  definition of properties of products and systems;  specification of maintenance requirements following protection and repair ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ This European Standard contains an Annex A (Informative) which provides guidance and background information on the Normative text BS EN 1504-9:2008 EN 1504-9:2008 (E) Scope This Part of EN 1504 sets out basic considerations for specification of protection and repair of reinforced and unreinforced concrete structures (including, for example, pavements, runways, floor slabs and pre-stressed structures) using products and systems specified in other Parts of the EN 1504 series or any other relevant European Standard or European Technical Approval This European Standard covers atmospherically exposed, buried and submerged structures This European Standard includes: a) the need for inspection, testing and assessment before and after repair; b) protection from causes of defects and their repair in concrete structures Causes of such defects may include: 1) mechanical actions, e.g impact, overloading, movement caused by settlement, blast, vibration and seismic actions; 2) chemical and biological actions from environments, e.g sulphate attack, alkali aggregate reaction; 3) physical actions, e.g freeze-thaw, thermal cracking, moisture movement, salt crystallisation and erosion; 4) 5) fire damage; ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ reinforcement corrosion resulting from: i) physical loss of the protective concrete cover; ii) chemical loss of alkalinity in the protective concrete cover as a result of reaction with atmospheric carbon dioxide (carbonation); iii) chloride (or other chemical) contamination of the concrete; iv) stray electrical currents conducted or induced in the reinforcement from neighbouring electrical installations c) repair of defects caused by inadequate design, specification or construction or use of unsuitable construction materials; d) providing the required structural capacity by: 1) replacement or addition of embedded or external reinforcement; 2) filling of cracks and voids within or between elements to ensure structural continuity; 3) replacement or addition of concrete or whole elements; e) waterproofing as an integral part of protection and repair; f) principles and methods of protection and repair, for example those listed in Table Site application is covered in Part 10 of this European Standard Further background information on the scope of this European Standard is given in Annex A (Informative) BS EN 1504-9:2008 EN 1504-9:2008 (E) Normative references The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies EN 206-1, Concrete — Part 1: Specification, performance, production and conformity EN 1504-1:2005, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 1: Definitions EN 1504-2:2004, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 2: Surface protection systems for concrete EN 1504-3:2005, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 3: Structural and non structural repair EN 1504-4:2004, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 4: Structural bonding EN 1504-5:2004, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 5: Concrete injection EN 1504-6:2006, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 6: Anchoring of reinforcing steel bar EN 1504-7:2006, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 7: Reinforcement corrosion protection ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ EN 1504-8:2004, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 8: Quality control and evaluation of conformity EN 1504-10:2003, Products and systems for the protection and repair of concrete structures — Definitions, requirements, quality control and evaluation of conformity — Part 10: Site application of products and systems and quality control of the works Terms and definitions For the purposes of this document, the terms and definitions given in EN 1504-1, EN 1504-2, EN 1504-3, EN 1504-4, EN 1504-5, EN 1504-6, EN 1504-7, EN 1504-8, EN 1504-10 and the following apply 3.1 defect unacceptable condition that may be in-built or the result of deterioration or damage 3.2 design life intended useful period of service under expected conditions of use of the concrete structure 3.3 maintenance recurrent or continuous measures that provide repair and/or protection 3.4 passivity state in which steel in concrete does not spontaneously corrode due to a protective oxide film BS EN 1504-9:2008 EN 1504-9:2008 (E) NOTE See A.3 3.5 protection measure that is intended to prevent or reduce the development of defects in the structure 3.6 repair measure that is intended to rectify defects in the structure 3.7 service life period over which the intended performance is achieved NOTE See A.3 3.8 substrate surface on which a protection or repair material is to be applied NOTE See A.3 Minimum requirements before protection and repair 4.1 General ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Clause outlines procedures that shall be undertaken to assess the current condition of a concrete structure before protection and repair General guidance is given in Annex A (informative) 4.2 Health and Safety The risks to health and safety from falling debris or local failure due to removing materials, and the effect of deterioration upon the mechanical stability of the concrete structure shall be assessed Where the concrete structure is considered to be unsafe, appropriate action shall be specified to make it safe before other protection or repair work is undertaken, taking into account any additional risks that may arise from the repair work itself Such action may include local protection or repairs, the installation of support or other temporary works, or partial or even complete demolition 4.3 Assessment of defects and their causes An assessment shall be made of the defects in the concrete structure, their causes, and of the ability of the concrete structure to perform its function The process of assessment of the structure shall include but not be limited to the following: a) the visible condition of the existing concrete structure; b) testing to determine the condition of the concrete and reinforcing steel; c) the original design approach; d) the environment, including exposure to contamination; BS EN 1504-9:2008 EN 1504-9:2008 (E) e) the history of the concrete structure, including environmental exposure; f) the conditions of use, (e.g loading or other actions); g) requirements for future use The nature and causes of defects, including combinations of causes, shall be identified and recorded (see Figure 1) NOTE A.4.3 Further guidance on the effect of design and construction errors on the durability of the structure is given in The approximate extent and likely rate of increase of defects shall then be assessed An estimate shall be made of when the member or concrete structure would no longer perform as intended, with no protection or repair measures (other than maintenance of existing systems) applied The results of the completed assessment shall be valid at the time that the protection and repair works are designed and carried out If, as a result of passage of time or for any other reason, there are doubts about the validity of the assessment, a new assessment shall be made ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Figure — Common causes of defects BS EN 1504-9:2008 EN 1504-9:2008 (E) A.2 Normative reference See Clause and Bibliography A.3 Terms and definitions These include terms that are not in common use in construction and which have a special meaning in this Annex A.3.1 Passivity When reinforcement is surrounded by uncontaminated alkaline concrete, the high alkalinity naturally present leads to the formation of a protective oxide layer on the steel surface, termed passivity This layer effectively reduces the risk of reinforcement corrosion to an insignificant level, despite the simultaneous presence of water and oxygen The protection afforded by the protective oxide layer is lost when the concrete carbonates to the depth of the reinforcement or when aggressive salts are present in sufficient quantities at the depth of the reinforcement This results in active corrosion in the presence of moisture and oxygen, which may lead to cracking and spalling of the cover To prevent loss of passivity, or where passivity has been lost, appropriate products and systems can be used to control corrosion of the steel reinforcement, in line with the principles of this European Standard A.3.2 Service Life ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ It is normally expected that a new concrete structure or, following intervention, a protected or repaired concrete structure will achieve its service life without significant unplanned deterioration and maintenance A.3.3 Substrate A substrate would normally require preparation, cleaning and testing prior to the application of products and systems for protection and repair (see EN 1504-10) A.4 Minimum requirements before protection and repair A.4.1 General A.4 is not a detailed guide to undertaking a structural appraisal or a condition assessment of the concrete structure To help users of this European Standard, Figure A.1 gives an example of the phases of a repair project 16 EN 1504-9:2008 (E) ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Figure A.1 — The phases of a typical repair projects 17 BS EN 1504-9:2008 EN 1504-9:2008 (E) Before any repair and protection work can start, a data collection exercise needs to be completed to establish the current condition of the structure, the maintenance history and the likely future performance Ideally, this should be undertaken in the context of a structure management strategy, which is discussed in more detail in Clause A.4.2 Health and Safety The structural assessment of deteriorated structures is governed by national standards, regulations and guidance and is not discussed further See also A.5.3.2 (Structural factors) and A.5.3.3 (Health and Safety factors) for information on the requirements before, during and after repair and protection works Where a risk to third parties exists, all loose and spalled material should be removed as part of the initial survey works A.4.3 Assessment of defects and their causes A.4.3.1 General A.4.3 provides background information on the assessment of defects and their causes and does not provide detailed comments on the individual subclauses in the normative text A.4.3.2 Defects and Causes Defects in concrete structures can result from inadequate design, specification, supervision, execution, and materials, including: ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ  inadequate structural design;  inadequate mix design, insufficient compaction, insufficient mixing;  insufficient cover;  insufficient or defective waterproofing;  contamination, poor or reactive aggregates;  inadequate curing Other defects may become apparent during service, including the effects of:  reinforcement corrosion;  severe climate, atmospheric pollution, chloride, carbon dioxide, aggressive chemicals;  foundation movement, impacted movement joints, overloading;  impact damage, expansion forces from fires;  erosion, aggressive groundwater, seismic action;  stray electric currents The common causes of defects in concrete and corrosion of reinforcement are summarised in Figure 18 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.4.3.3 Condition Assessment Prior to repair work commencing, all previous information on the structure should be collated and reviewed When defects are observed, additional testing and assessment should be carried out to establish the cause and extent of the defects and to predict future performance The condition of the concrete and reinforcement should be established and documented and the data stored in a management system A typical assessment would include insitu testing for cover to reinforcement and carbonation depth, drilled dust sampling to determine the chloride ion content and profile and the presence of other deleterious substances, and cores for physical, chemical and petrographic analyses Electrochemical testing of the reinforcement (e.g by half-cell potential technique) may be required in certain instances where elevated chloride ion contents have been measured and active hidden corrosion may be present Generally, corrosion of embedded reinforcement ultimately results in cracking and spalling of the concrete cover However, it should be kept in mind that active corrosion may occur for a considerable time before cracks appear and also that, under certain conditions, the corrosion may not be expansive and therefore may not result in cracking This being the case, electrochemical testing should be considered because it is able to detect active corroding reinforcement even though there are no outward visible signs Such hidden damage also needs to be considered in the structure management strategy (see A.5) The assessment of existing condition and prediction of future performance should preferably include consideration of previous tests made at suitable intervals and information on the history of the concrete structure, for instance construction, use and management (where available) ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ An assessment is normally carried out as a separate operation before the start of the protection and repair works Assessments of the structure that are carried out some time before the design of the repair works is considered may not represent the contemporary condition and structural capacity at the time the repair works are designed In such cases the assessment needs to be updated before the protection and repair works are designed In all cases, it is essential to assess the full extent and causes of the defects A condition assessment may be undertaken in more than one stage For example, a preliminary stage may be required to provide immediate advice on the safety of the concrete structure and any risk to third parties, with a more detailed assessment undertaken immediately before the works are designed The assessment of defects, the prognosis for their further development and the structural assessment should be recorded A.4.3.4 Structural Appraisal As part of the structural appraisal, the properties of the concrete (e.g compressive strength and elastic modulus) and the reinforcement detailing (e.g bar size, type, spacing and cover) may need to be verified through testing Recalculation of the remaining load capacity in the deteriorated state may be needed A.4.3.5 Qualifications of assessors Condition assessments and structural appraisals are often carried out in advance of the repair process set out in this European Standard and sometimes before it has been recognised that a problem exists All assessments should be made by suitably qualified personnel with knowledge of investigation methods, structural design, maintenance, material technology and of the mechanisms which can contribute to the deterioration process of concrete structures It should be noted that national, federal or local rules for assessors may apply The competence of personnel designing, specifying and executing concrete repair works is set out at A.9 19 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.5 Protection and repair within a structure management strategy A.5.1 General A structure management strategy is not chosen on technical grounds alone, but also on economic, functional, environmental and other factors, and most importantly the owner’s requirements for the structure The design life of the repaired concrete structure is a key consideration in the design of the protection and repair system Options range from those that can restore the design life of the concrete structure in a comprehensive single operation, to simpler options that may require repeated maintenance or where components of the repair may need to be reapplied (e.g surface protection systems), as illustrated in Figure A.2 below ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Key X Y A B Asset condition Life of the asset Critical condition Target life Ideal life curve Actual deterioration curve Projected deterioration Repair based on: Restoring to initial state x2 Maintaining current state Figure A.2 — Typical repair cycles over the life of a deteriorating asset 20 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.5.2 Options Maintaining or restoring safety is an essential requirement of a structure management strategy A range of options may be available to meet this prerequisite These options should normally be assessed for their efficacy over the remaining life of the structure, termed life cycle costing Consideration of the options and their consequences will generally include examination of different aspects, for example initial cost, maintenance costs and the possible need to introduce restrictions on the use of the structure Each option is likely to have a different level of future deterioration risk When choosing options for protection and repair systems, an important consideration is the life to first maintenance of the individual products, as they may not last for the design life of the concrete structure Factors such as access to the works and the renewal and reparability of protection and repair systems are important considerations A.5.3 Factors 5.3 lists the factors that need to be considered when making an informed judgement on the relative costs and benefits of the possible technical options for repair A.5.3.1 General a) Correct monitoring and maintenance of the protection and repair works will result in a longer service life for both the works and the structure b) The nature and use of the structure may have a significant influence on the choice of the management strategy, the repair principles and the equipment and systems to be used, particularly noise and dust generation from preparing the substrate (e.g office buildings, hospitals, etc) c) In the case of premature deterioration, service life can be extended by protection and repair However, deterioration is an on-going process and an informed choice may have to be made between: ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ 1) carrying out protection and repair which will extend the service life to attain the original design life; and 2) carrying out protection and repair which will extend the life for a lesser period in the knowledge that their will be additional protection and repair costs in the future; d) properties and possible methods of preparation of the existing substrate can have an effect on the final appearance of the protected and repaired structure A.5.3.2 Structural factors The structural appraisal prior to repair can be extended to predict the effects of the repair works on the structural capacity, both during repair and after the works have been completed Particular attention needs to be paid to the volume of concrete and reinforcement that is cut away from loadbearing structural members and the effect this will have on the future structural capacity An example is the removal of concrete from compression members, altering load paths such that the repairs are effectively not loadbearing Should this be of structural significance, repair principles should be considered that minimise the breakout and repair and/or utilise propping to relieve dead load during the repair A.5.3.3 Health and safety factors a) An important stage in the structure management strategy is to assess the structural consequences from any deterioration and the repair process itself before work begins (see also 5.3, b)) b) health and safety requirements are given in national regulations and guidelines 21 BS EN 1504-9:2008 EN 1504-9:2008 (E) c) the materials and methods used in the selected repair principles will potentially affect operatives as well as occupiers, users or third parties Examples include: products that contain harmful or malodorous components; creation of noise, dust and vibration; water or airborne debris from preparation processes; or plant movements A.5.4 Choice of appropriate strategy The structure management strategy should reflect the client’s requirements for the design and service life of the structure and the maintenance and repair options, which given which management strategy should be developed The initial causes of the defects need to be identified Generally, protection and repair will deal successfully with the causes and consequences of defects In some cases, other issues may be contributing to the deterioration (e.g blocked drains on bridge decks that lead to chloride contamination of the substructure) and it may be necessary to deal separately with these issues before a successful repair can be carried out If correction of the cause is not possible (e.g in a marine environment), the protection and repair must be designed to resist the cause as far as possible A.6 Basis for the choice of protection and repair principles and methods A.6.1 General Selection of appropriate repair principles is the most important part in the design of the repair project Several approaches may be possible, with the final selection based on a variety of factors (see A.5.1) Suitable repair methods should be specified for all chosen principles Where possible, the specification should include the appropriate performance requirements for products and systems for the intended use Producers may need to be consulted to verify that their products or systems fulfil the intended requirements ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Products and systems for the intended use should be selected taking into account the condition of the substrate and the assessment of defects and their causes as detailed in 4.3 of this European Standard A.6.2 Principles and methods of protection and repair Several protection and repair methods may be chosen in combination Care needs to be taken to consider the possible adverse effects of the chosen methods and the consequences of interactions between them Examples of possible adverse effects include: a) hydrophobic impregnation system used to reduce the moisture content of concrete, which may increase the rate of carbonation; b) surface coating, which may entrap moisture, leading to a breakdown in adhesion or reduced frost resistance; c) post-tensioning, which can cause tensile stresses in the structures; d) electrochemical methods, which may cause embrittlement of susceptible prestressing steel, alkali aggregate reaction with susceptible aggregates, a decrease in frost resistance due to increased moisture contents, or, if under water, corrosion in adjacent structures or vessels Products and systems should be compatible with each other and with the original concrete structure Where there is a history or risk of reinforcement corrosion, Principles to 11 in Table should be considered in addition to Principles to 6, because the expansive effects of ongoing reinforcement corrosion may damage concrete in the future if left unchecked 22 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.6.2.1 A.6.2.1.1 Principles and methods related to defects in concrete General A.6.2.1 provides background information on repair Principles to in Table and does not provide detailed comments on the individual subclauses in the normative text A.6.2.1.2 Principle - Protection against ingress Protection against ingress includes measures to reduce the porosity or permeability of the concrete surface This is achieved by treating the concrete surface (e.g using a surface protection system to EN 1504-2) or sealing cracks (e.g injection of cracks to EN 1504-5, or by bandaging or filling the surface) Normal structural cracks have widths that are within the limits defined in EN 1992-1-1, which open and close in response to loads under the control of the reinforcement in concrete Overload or under-design of a structure may result in structural cracks that exceed the limits defined in EN 1992-1-1 Non-structural cracks may form in the concrete for a number of reasons, e.g plastic shrinkage or settlement, heat of hydration, thermal contraction and these may be much wider than structural cracks and may open and close in response to both structural loads and environmental effects such as temperature changes Cracks of any width may cause deterioration and the consequences should be considered Where there is a danger that corrosive contaminants will penetrate the concrete at cracks, consideration should be given to protecting cracks that are currently free from contamination by filling them in accordance with method 1.4 Once the causes, ranges of movements and effects have been established, including whether the crack is live (e.g opening and closing in response to loads or thermal effects) or dead, then options for repair can be selected from methods 1.1 to 1.8 Some surface protection systems specified in EN 1504-2 are suitable for application over live normal structural cracks but few will bridge wide, non-structural cracks, which may need to be sealed by other methods ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Some cracks in hardened concrete form as a result of reinforcement corrosion These cracks are often the first visual sign that there is a corrosion problem Cracks caused by corrosion must not be repaired simply by filling or sealing These defects should be repaired by methods that apply Principles to 11 The possibility of further movement of the cracks adversely affecting the repair should be considered Further information concerning live and dead cracks is given in EN 1504-5 It should be noted that method 1.8 (applying membranes) may be equally applicable to Principles 2, & A.6.2.1.3 Principle - Moisture control Moisture control is used in the repair of concrete to control adverse reactions by allowing concrete to dry, as well as preventing moisture build-up Adverse reactions may include alkali-silica reaction and sulfate attack Saturated concrete may also be susceptible to freeze-thaw damage Surface protection systems applied to vertical and soffit surfaces should be permeable to water vapour to allow moisture to escape from the concrete Upper surfaces of horizontal concrete members (e.g a suspended floor slab in a car park) may have an impermeable surface protection system applied Surface protection systems should not normally be applied to concrete containing excess moisture and product manufacturers should advise on appropriate application conditions A.6.2.1.4 Principle - Concrete restoration Concrete restoration is normally carried out using either hand-applied patch repairs, or recasting with flowing concrete or mortar, or applying concrete or mortar by spraying The scope of EN 1504-3 includes materials 23 BS EN 1504-9:2008 EN 1504-9:2008 (E) suitable for structural and non-structural repair Replacing of elements may include materials other than reinforced concrete Further advice on sprayed concrete is given in EN 14487-1 A.6.2.1.5 Principle - Structural strengthening It is essential when using Principle that all stresses associated with a repair and the original or deteriorated structure are considered Certain systems may impose additional stresses on the repaired structure, resulting in changes in the original structural function While injecting or surface sealing cracks will not structurally strengthen a structure, injection may be used to restore the element to its structural condition prior to cracking (e.g when temporary overloading has occured) A.6.2.1.6 Principle – Increasing physical resistance Removal of the concrete surface by physical actions, such as impact or abrasion, may affect the structural or durability performance of the structure The causes need to be identified and physical protective measures may need to be taken to reduce their effects, as well as applying the repair methods A.6.2.1.7 Principle – Increasing resistance to chemicals Where concrete has been attacked, the chemicals will need to be identified and suitable preventive measures may need to be taken, as well as applying the repair methods The resistance of concrete to different classes of environmental attack is defined in EN 206-1 This European Standard covers products and systems which may protect the concrete against environmental attack by chemicals listed in EN 206-1 and to severe chemical attack by chemicals listed in EN 13529 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Under certain conditions, soils, water treatment works and sewage can generate acids or sulfates by bacterial action that can promote attack on the concrete and reinforcement A.6.2.2 A.6.2.2.1 Principles and methods concerning reinforcement corrosion General A.5.2.2 provides background information on repair Principles to 11 in Table and does not provide detailed comments on the individual clauses in the normative text Reinforcement may be at risk of corrosion for a wide variety of reasons, including poor quality or missing concrete cover, contamination e.g by chlorides, advancing carbonation, or other physical, chemical or electrochemical effects A.6.2.2.2 Carbonation Where the reinforcement is protected by some remaining uncarbonated cover (as indicated by the carbonation test - see EN 14630), methods 1.2, 1.3 and 1.7 (see Table 1) are examples that may be used to reduce access of carbon dioxide to the concrete Where the reinforcement is in contact with carbonated concrete the passivity will have been lost and corrosion may begin A variety of methods can be used to control corrosion in this situation, using one or more Principles and Methods As well as carbon dioxide, other air-borne acidic pollutants, such as sulfur dioxide, can attack both concrete and reinforcement in areas where pollution is high, for example in chimneys 24 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.6.2.2.3 Chlorides or other corrosive contaminants Corrosion caused by the ingress of chloride ions is more difficult to treat than corrosion caused by carbonation The presence of chloride ions at the depth of the reinforcement breaks down the passive layer in uncarbonated concrete and allows corrosion to begin Where elevated chloride ion contents have been detected (as indicated by the chloride ion content test - see EN 14629), then there is a risk that reinforcement corrosion can occur The concentration that triggers corrosion varies in each individual case and depends on many factors including the cement type, w/c-ratio, the source of chloride, the alkalinity of the concrete and the exposure environment The source of the chloride ion is also important, in particular whether the chloride was cast into the concrete at the time of construction, or has entered the concrete subsequent to hardening For a given chloride ion content, chloride which has entered the concrete from an external source is more aggressive in terms of corrosion risk Corrosion risk can also be increased by carbonation of concrete containing relatively low concentrations of chloride ion Traditionally, a figure of 0,4% by weight of cement was used as the threshold above which reinforcement corrosion would occur More recent research shows the figure can be much lower than this, sometimes below 0,2%, although in certain environmental conditions much higher values can be tolerated Therefore it is important to calibrate the risk of corrosion against the actual prevailing conditions of each structure and no “safe” limit should be assumed Reinforcement corrosion can also be caused by halides other than chlorides, or other water-soluble chemicals ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Treatment of local areas of concrete that are contaminated by chloride ion can be successfully carried out by patch repair that removes all the contaminated concrete However, where contamination is extensive, treatment of areas of damage alone will not provide a lasting repair solution Areas repaired with new mortar or concrete can initiate corrosion in adjacent areas of contaminated concrete (often termed incipient anode or ring anode effect) In these situations, additional methods will need to be considered if corrosion is to be arrested, such as those given in Principles to 11 A.6.2.2.4 Principle - Preserving or restoring passivity A.6.2.2.4.1 General The Methods relate to treating or replacing the concrete surrounding the reinforcement to reduce the risk of corrosion A.6.2.2.4.2 Method 7.1 Increasing cover with additional mortar or concrete Where the reinforcement is passive, an additional layer of mortar or concrete may be added over carbonated concrete to provide additional protection A.6.2.2.4.3 Method 7.2 Replacing contaminated or carbonated concrete Where reinforcement has lost protection as a result of carbonation or chloride ion ingress, the structure may be repaired by replacing the contaminated or carbonated concrete with new concrete or mortar in accordance with method 7.2 Additional protection may be required in the form of a surface protection system in accordance with Principle In the case where chloride ions remain in the concrete, there will be a risk of recontamination of the repair by diffusion and incipient anodes forming on reinforcement in the surrounding concrete In these situations, other repair methods may need to be considered 25 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.6.2.2.4.4 Method 7.3 Electrochemical realkalisation of carbonated concrete Where the reinforcement is active or passive, additional corrosion protection can be provided by electrochemical realkalisation, which raises the alkalinity of carbonated concrete and provides passivity to the reinforcement This method is applied according to the principles of CEN/TS 14038-1 The application of suitable coatings may extend the life of the treatment A.6.2.2.4.5 Method 7.4 Realkalisation of carbonated concrete by diffusion There is limited experience with this method, but different approaches have been used in some parts of Europe in certain situations One approach involves application of a highly alkaline cementitious concrete or mortar to the surface of carbonated concrete, allowing the concrete to be re-alkalised through diffusion from the surface A.6.2.2.4.6 Method 7.5 Electrochemical chloride extraction Where the reinforcement is active or passive due to chloride ion ingress, additional corrosion protection can be provided by electrochemical chloride extraction, which reduces the chloride ion content in the concrete surrounding the reinforcement and provides passivity Guidance on this method will be contained in CEN/TS 14038-2 (in preparation) covering chloride extraction, which is currently in preparation A.6.2.2.4.7 Principle - Increasing resistivity ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Internally, in dry buildings, corrosion is seldom a problem even if the concrete is carbonated at the depth of the reinforcement This is because the low moisture content in enclosed buildings tends to raise the resistivity of the concrete to a level where the corrosion rate is insignificant In some situations, the resistivity of external concrete may be reduced through the application of ventilated external cladding, water-repellent surface treatments, pore-filling impregnation or surface coatings (Principles and 2) The technique for reducing the corrosion rate by limiting the moisture content, for example by over-cladding, is limited to situations where concrete can be prevented from taking up water from other sources Also, the escape of moisture from the concrete should not be impeded With chloride-contaminated concrete, the risk of corrosion is more significant Methods that increase the resistivity of the concrete may not be adequate in themselves to reduce corrosion of the reinforcement In this situation, additional repair Principles may be needed The technique for reducing the corrosion rate by limiting the moisture content, for example by over-cladding, is limited to situations where concrete can be prevented from taking up water from other sources A.6.2.2.4.8 Principle - Cathodic control Principle relies upon restricting access of oxygen to all potentially cathodic areas, to the point when corrosion cells are stifled and corrosion is prevented by the inactivity of the cathodes A.6.2.2.4.9 Principle 10 - Cathodic protection Cathodic protection is especially appropriate where chloride contamination is significant, or carbonation to the depth of the reinforcement is extensive, resulting in a high risk of corrosion of reinforcement Impressed current cathodic protection applied according to EN 12696 can control corrosion regardless of the level of chloride contamination in the concrete and limits the amount of concrete removal to that physically damaged by corrosion of underlying reinforcement Its long term effectiveness depends on adequate monitoring and maintenance 26 BS EN 1504-9:2008 EN 1504-9:2008 (E) Cathodic protection is effective for achieving long-term corrosion control and counteracts the incipient anode problem and the effect of concrete contamination (see EN 12696) There are many different types of external anode systems used in cathodic protection, some of which use an impressed current from an external power source, while others use galvanic (sacrificial anode) action A.6.2.2.4.10 Principle 11 - Control of anodic areas Where contamination of the concrete is extensive, but it is not possible to remove all contaminated concrete, incipient anode formation can be controlled by treating the surface of the reinforcement in the patch repair to prevent corrosion Coatings can be applied directly to the reinforcement where it is exposed as part of concrete restoration These coatings can contain active pigments, which may function as anodic inhibitors or by sacrificial galvanic action Other types of coating can form barriers on the surface of the reinforcement This method can only be effective if the reinforcement is prepared to be free of corrosion and the coating is complete (i.e the bar must be completely encapsulated and the coating is defect-free) The method should not be considered unless the whole of the circumference of the reinforcing bar can be coated The effect of the coating on bond between the reinforcement and concrete should also be considered Alternatively, corrosion inhibitors can be used that chemically change the surface of the steel or form a passive film over it Corrosion inhibitors can be introduced either by addition to the concrete repair product or system, or by application to the concrete surface followed by migration to the depth of the reinforcement Inhibitors that are applied to the surface of the concrete must penetrate the concrete down to the level of the reinforcement to take effect There is currently no standard for inhibitors, so evidence of the effectiveness of any such product should be obtained before specifying its use ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Note that some corrosion inhibitors work by control of both anodic and cathodic areas (see Principle 9) In severe conditions, additional repair principles may be required A.6.2.3 Protection against and repair of reinforcement corrosion by methods not specifically mentioned in this European Standard Concrete protection and concrete repair are rapidly developing technologies and new methods of protection and repair are frequently proposed, developed and applied on a trial basis This is especially true where reinforcement corrosion is the cause of the defects Some such methods may not have an extensive history of previous use, yet may prove to be effective in appropriate circumstances A.7 Properties of products and systems required for compliance with the principles of protection and repair To avoid any possible confusion, it is intended that the properties of a system for concrete repair should be tested and compared with the relevant performance requirements in EN 1504-2 to -7 It is not intended that each component product of a system is tested and evaluated individually against the performance requirements unless the products can be used by themselves to meet the performance requirement For example, the properties of a surface protection system for a car park deck may contain multiple products such as a primer, elastic layer, sealing layer and wearing layer, each layer being of the thicknesses specified by the manufacturer Compliance with the performance requirements is measured on the system applied in accordance with the manufacturer’s recommended values and this would be stated alongside the CE Conformity symbol on the packaging of the products that comprise the system Particular attention is required to the temperature and humidity conditions at application, because most repair products have been formulated to perform within a given range of ambient application conditions Application guidance is given in EN 1504-10 27 BS EN 1504-9:2008 EN 1504-9:2008 (E) A.8 Maintenance following completion of protection and repair Upon completion of concrete repair works, a maintenance management system should be implemented to ensure that the required future maintenance is carried out Parts of the protected or repaired concrete may have an expected service life that is short in comparison with the rest of the concrete structure Examples include surface protection systems, sealants, and weatherproofing materials Should the integrity of the structure depend on the performance of such products and systems, it is essential that they are regularly inspected, tested and renewed if necessary The following listing gives information for future maintenance which should be included: a) an estimate of the expected remaining design life of the concrete structure; b) identification of each product and system where the design life is expected to be less than the remaining design life of the concrete structure; c) the date at which each product and system is next to be inspected or tested; d) the method of inspection to be used, including how results are to be recorded and how future inspection dates are to be decided; e) a specification for systems with continuous treatment and monitoring, for example as used in an impressed current cathodic protection system; f) a statement of precautions to be taken or restrictions to be applied, for example maintenance of surface water drainage, maximum pressure for water washing or prohibition of the use of deicing salt ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ A.9 Health, safety and environment No further information A.10 Competence of personnel Personnel should be appointed who are familiar with protection and repair of concrete works and recognised as competent This requirement requires to all persons involved in the repair process, including repair scheme designers, repair contractors and repair works inspectors A quality system should be employed by the repair contractor to ensure that the specified quality requirements are met and that the right repair methods are used Appropriate arrangements should be made for acceptance inspection All documents relating to the repair work should be stored in a suitable project management system 28 BS EN 1504-9:2008 EN 1504-9:2008 (E) Bibliography [1] prEN 13670, Execution of concrete structures [2] EN 13529, Products and systems for the protection and repair of concrete structures – Test methods – Resistance to severe chemical attack [3] EN 1992-1-1, Eurocode 2: Design of concrete structures — Part 1-1: General rules and rules for buildings [4] EN 12696, Cathodic protection of steel in concrete [5] EN 14629, Products and systems for the protection and repair of concrete structures – Test methods – Determination of chloride content in hardened concrete [6] EN 14630, Products and systems for the protection and repair of concrete structures – Test methods – Determination of carbonation depth in hardened concrete by the phenolphthalein method [7] CEN/TS 14038-1, Electrochemical realkalization and chloride extraction treatments for reinforced concrete — Part 1: Realkalization [8] prCEN/TS 14038-2, Electrochemical re-alkalisation and chloride extraction treatments for reinforced concrete – Part 2: Chloride extraction (in preparation) [9] EN 14487-1, Sprayed Concrete - Part 1: Definitions, specifications and conformity ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ 29 BS EN 1504-9:2008 BSI - British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and 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